1. Field of the Invention
This invention relates to washing machines. More particularly, it relates to washing machines having improved washing performance and easier laundry removal.
2. Discussion of the Related Art
Washing machines operate by revolving a vessel that holds laundry, water, and detergent such that friction, water current, and chemical action clean the laundry. While there are various types of washing machines, common types include drum type washing machines and pulsator type washing machines.
The structure of a typical drum washing machine is schematically illustrated in FIG. 1. As shown, a drum washing machine includes a cabinet 1 having a front door 2, a tub 3 inside the cabinet 1 that retains wash water, and a rotating drum 4 inside the tub 3 that retains laundry. A motor 5 behind the tub 3 is coupled by a driving shaft 6 to the drum 4. Also, a suspension system 7 retains the tub 3 within the cabinet 1 such that the position of the tub 3 can fluctuate slightly.
Still referring to FIG. 1, the driving shaft 6 is coupled to the drum 4 by a spider 8 (which can be tripod-shaped). Additionally, as shown, a number of lifters 10 are mounted on a wall of the drum 4. When the motor 5 rotates the drum 4, the lifters 10 also rotate. Laundry is lifted upward by the lifters 10 until the laundry freely falls down. Continuous rotation causes the laundry to continuously move up and down. Such laundry movement produces a good laundry cleaning action.
FIG. 2 illustrates a typical lifter 10 in more detail. The lifter 10 includes a pair of protrusions 11 that have different heights and that are separated by a valley 12. Coupling hooks 13 at the bottom of the lifter 10 can couple the lifter 10 to the drum 4.
While generally successful, the lifters 10 do not provide optimal washing performance. One reason for this is that the lifters 10 generally have flat (or at least smooth) surfaces that fail to maximize laundry friction. Thus, friction-induced cleaning is limited. Such limited cleaning action occurs not only in drum type washing machines, but also in pulsator type washing machines. The pulsator type cleans both by water flow and by laundry friction. Yet, the widely used pulsator type washing machine also uses generally flat (or at least smooth) contact surfaces. Again, this limits the attainable cleaning action.
While generally successful when cleaning laundry, the lifters 10 become obstacles when removing laundry. Centrifugal forces exerted during a dehydration cycle forces laundry against the wall of the drum 4 and into the valley 12. This causes the laundry to adhere to the drum 4 such that the laundry can be difficult to remove.
A modification to the standard drum type washing machine is the slant-drum washing machine. In such a machine the drum 4 is tilted downward. This reduces the difficulty of inserting and removing laundry. However, in slant-drum 4 washing machines the laundry tends to gather toward the rear of the drum 4 such that the lifters 10 fail to smoothly move the laundry. Thus, cleaning performance is reduced.
Therefore, washing machines having improved washing performance obtained by increasing the friction of lifters with laundry would be beneficial. Also beneficial would be a washing machine having easy laundry removal after dehydration cycles. Also beneficial would be a slant-drum washing machine having a reduced tendency for laundry to congregate at the back of the drum. Even more beneficial would be a drum washing machine with improved laundry friction and ease of laundry removal.